Lighting systems are generally designed to use artificial (electric) lighting to provide an appropriate level of illumination within a space without respect to the availability of natural lighting (daylight). In this way it can be guaranteed that lighting levels will not fall below target levels when daylight is not present—such as at night or on cloudy days. However, when daylight is present, the sum of the availing daylight and the light provided by electric lighting can significantly exceed target illumination levels, which in turn wastes electrical energy. “Daylight harvesting” systems recognize when the presence of daylight has caused lighting levels to exceed their target levels and automatically reduce the electric lighting levels accordingly, resulting in reduced energy consumption.